In the treatment of fluids such as a liquid, a gas, etc., membrane separating apparatuses using tubular or capillary membranes are used for the separation of solvents or solutes from feeds by reverse osmosis, ultrafiltration or microfiltration; the separation of gases; etc.
As the above-described membrane separation apparatus, a membrane separation apparatus is known, in which a plurality of tubular or capillary membranes are inserted into a cylindrical case, the membranes each other and the membranes and the case, at the end portions of the membranes, are sealed and fixed with a casting resin, and the membranes have both open ends. FIG. 1 illustrates one embodiment of the specific structures thereof.
Referring to FIG. 1, a plurality of tubular or capillary membranes 1 are bundled in a parallel state with each other and inserted into a cylindrical case 2 provided with an outlet 7 for a membrane permeated fluid, both end portions of the tubular or capillary membranes are integrally bonded with a casting resin 3 to each other and fixed to the case 2, the membranes 1 have both open ends, a cap 8 having a nozzle 4 for a feed inlet and a nozzle 6 for a membrane permeated fluid outlet is provided at one end of the case 2, and a cap 9 having a nozzle 5 for a concentrated fluid outlet is provided at the other end thereof.
In the case that a feed is separation treated with such a membrane separation apparatus, the apparatus is generally used in longitudinal arrangement mode such that the axis of the case 2 lies in vertical direction, taking into consideration the arrangement area, the exchange operation efficiency or the like. The feed is fed from the inlet nozzle 4, the concentrated fluid is flown out of the outlet nozzle 5, and the membrane permeated fluid obtained is taken out from the outlet nozzle 6 for the permeated fluid.
The conventional membrane separation apparatus described above has following problems:
(i) The inlet and the outlet of the feed are positioned at both ends of the case, so that the pipe arrangement becomes complicated in longitudinal and vertical directions when arranging the apparatus in longitudinal arrangement mode.
(ii) The inner and outer faces of the casting resin 3 are formed perpendicular to the axis of the case 2, so that foams or membrane permeated fluids retain in the neighborhood of the inner face 3a of the casting resin 3 and microorganisms or the like grow at this retention portion to contaminate the membrane permeated fluid.
(iii) Due to the contamination of the membrane permeated fluid by the generation of foams or the retention of the membrane permeated fluids, performance of the membrane separation apparatus is lowered.
(iv) The outlet 6 for the permeated liquid is provided close to the outer periphery of the tubular or capillary membranes 1, so that the flow of the membrane permeated fluid from the tubular or capillary membranes 1 becomes maximum in the neighborhood of the outlet 6 for the membrane permeated liquid and the tubular or capillary membranes 1 will be damaged around this portion.